New (p, ρ, T) data for carbon dioxide - Nitrogen mixtures from (250 to 400) K at pressures up to 20 MPa

Highlights: → Densities of two mixtures of nitrogen and carbon dioxide are reported. → Experimental data are compared with calculated densities from the equation of state. → Experimental data agree with the equation of state for low pressures above 300 K. → The equation of state shows higher deviations than expected at high pressures. - Abstract: Comprehensive (p, ρ, T) measurements on two binary mixtures (0.10 CO2 + 0.90 N2 and 0.15 CO2 + 0.85 N2) were carried out in the gas phase at seven isotherms between (250 and 400) K and pressures up to 20 MPa using a single sinker densimeter with magnetic suspension coupling. A total of 69 (p, ρ, T) data for the first mixture and 69 (p, ρ, T) data for the second are presented in this article. The uncertainty in density was estimated to be (0.02 to 0.15)%, while the uncertainty in temperature was 3.9 mK and the uncertainty in pressure was less than 0.015% (coverage factor k = 2). Experimental results were compared with densities calculated from the GERG equation of state and with data reported by other authors for similar mixtures. Results yielded that, while deviations between experimental data and values calculated from the GERG equation were lower than 0.05% in density for low pressures, the relative error at high pressures and low temperatures increased to about (0.2 to 0.3)%. The main aim of this work was to contribute to an accurate density data base for CO2/N2 mixtures and to check or improve equations of state existing for these binary mixtures.